It is known in fuel storage and delivery that it is commonly necessary to vent a fuel tank to relieve vapor pressure build-up which may occur when the fuel tank cap is in place and to permit the escape of air during normal filling operations when the fuel tank cap is removed. Thus, it is known to use an evaporative control system. A typical evaporative control system vents fuel vapor to a vapor storage canister, such as a carbon canister. It is also important to ensure that fuel vapors and/or raw fuel from the tank do not flood the canister during normal engine operation or during filling. Conventional designs for evaporative control systems seek to minimize the canister volume by protecting against fuel tank vapor generation and increasing engine purging of the canister.
Until recently, evaporative emission controls were generally not required for use in connection with small engine fuel tanks. However, current environmental control laws and regulations may now require that fuel tank systems for small engines include safeguards to prevent the excessive escape of fuel vapors under normal operating conditions and to prevent the escape of raw fuel from the tank in the event of a roll inversion. The compact size of such engines can create a particular challenge.